Method for separating liquid from solid substances and storing the solid substances

ABSTRACT

Apparatus for separating liquid-solid mixtures such as water from ion-exchange resins and mud in connection with the operation of a nuclear power plant, or separating other mixtures such as acid or alkali containing liquids, and thereafter storing the separated out solids all in one and the same vessel. Located within the vessel which is initially open at the top, and in radially spaced relation from the vessel wall is a filter component in the form of a cylindrical sieve or filter bag. The liquid-solid mixture is introduced into the filter component and the liquid component filters through the wall of the sieve leaving the solids within the filter. The liquid is then drawn off from the vessel by a suction pipe, after which the suction pipe is then removed and the vessel is then closed tightly by a cover member provided for the top. If desired, the vessel can be centrifuged to further remove the water component from within the filter, or compressed air can be introduced into the interior of the filter to serve the same purpose. If the solids are ionexchange resins which are radioactive, a water and/or ionizing radiation-absorbing agent such as a cement broth may be filled into the cavities remaining in the vessel between its wall and the filter component.

ilnited States Patent aumann et al.

METHOD FOR SEPARATING LIQUID FROM SOLID SUBSTANCES AND STORING THE SOLIDSUBSTANCES Inventors: Gustav Baumann, Untersiggenthal; GerhardHentschel, Neuenhof, both of Switzerland Assignee: AktiengesellschaftBrown, Boveri & Cie,

Baden, Switzerland Filed: Feb. 3, 1970 Appl. No.: 7,380

Field of Search ..210/416, 380, 266, 484, 452, 210/453, 454, 474, 29,448, 364, 398, 495, 66, 499

References Cited UNITED STATES PATENTS 9/1908 Barnes ..210/454 X 2/1920Wait ..210/452 X 9/1920 Hills ..210/452 1 Apr. 25, 1972 PrimaryExaminer-.1. L. De Cesare An0rney-Pierce, Schefiler & Parker [57]ABSTRACT Apparatus for separating liquid-solid mixtures such as waterfrom ion-exchange resins and mud in connection with the operation of anuclear power plant, or separating other mixtures such as acid or alkalicontaining liquids, and thereafter storing the separated out solids allin one and the same vessel. Located within the vessel which is initiallyopen at the top, and in radially spaced relation from the vessel wall isa filter component in the form of a cylindrical sieve or filter bag. Theliquid-solid mixture is introduced into the filter component and theliquid component filters through the wall of the sieve leaving thesolids within the filter. The liquid is then drawn off from the vesselby a suction pipe, after which the suction pipe is then removed and thevessel is then closed tightly by a cover member provided for the top. Ifdesired, the vessel can be centrifuged to further remove the watercomponent from within the filter, or compressed air can be introducedinto the interior of the filter to serve the same purpose. If the solidsare ionexchange resins which are radioactive, a water and/or ionizingradiation-absorbing agent such as a cement broth may be filled into thecavities remaining in the vessel between its wall and the filtercomponent.

1 Claim. 2 Drawing Figures Patented April 25,, 1972 3,658,179

INVHVTORJ Gusau Baumavm BY Gerhard Hen'tscheL,

METHOD FOR SEPARATING LIQUID FROM SOLID SUBSTANCES AND STORING THE SOLIDSUBSTANCES This application is a continuation of application Ser. No.689,440, filed Dec. 11, 1967, now abandoned.

The present invention concerns an apparatus for separating a liquid fromsolid substances contained therein and for the subsequent storage of thesolid substances in a tight vessel.

If, for example, water is obtained in the operation of a nuclear powerplant which contains ion exchange resins and filter mud, the water mustbe separated from the solid substances so that the latter can beenclosed in tight vessels and stored, for example, because they areradioactively contaminated.

The separation of the water from the solid substances and the subsequentstorage is usually so effected that the spent ion exchange-resins andthe filter mud contained in the water are conducted into collectingtanks in which the solid substances can settle and from which the clearwater is drained off. If excessive radioactivity prevents immediateprocessing of the resins, they are stored in so-called decaying tanksuntil at least the short-lived radioactive isotopes have disintegratedto a great extent. Since the settled ion exchange resins and the filtermud still contain large amounts of excess water, the settled solidsubstances are mostly fed to a centrifuge and separated therefrom thewater, particularly in order to reduce the volume. Solid substancestreated in this manner are subsequently placed in tight vessels whichare stored in a suitable place until the radioactivity has died out.

The known methods and apparatus have the disadvantage, however, thatthey require high investment costs, that they contain moving andmechanically highly stressed parts, which involves a greatersusceptibility to trouble, and that the multiple transportation of thewater and/or of the solid substances is complicated and, because of theradioactive impurities, dangerous. In particular the transportation ofthe finely ground resins, as they are now used, from the separator tothe storage tank presents some difficulties. Finally, the constantlyused apparatus and devices require expensive attendance, which isrendered very difficult by the presence of the radioactive impurities.

The object of this invention is to eliminate the above mentioneddisadvantages. According to the invention the apparatus is characterizedby a container whose top side is at least partly open, which can besealed tightly with a cover, and which is equipped for filtering andstorage; also a filter for separating the liquid from the solidsubstances, which is so arranged inside the vessel that the bottom ofthe vessel remains at least partly free for collecting the liquid aswell as by a device for removing the liquid from the vessel.

The invention will be described more fully below on the basis of theattached drawings, wherein:

FIG. 1 shows schematically an apparatus according to the invention witha screen as a filter means; and

FIG. 2 shows schematically another embodiment of the apparatus with afilter bag.

According to FIG. 1, a cylindrical sieve 2 is arranged in a storagevessel 1, which can be, for example, a commercial steel barrel. Theintrinsic strength of sieve 2 is also selected that it isself-supporting and hence can stand freely on the bottom 3 of thevessel 1. Besides, its outside diameter is so much smaller than theinside diameter of vessel 1, that a movable vertical suction pipe 4 canbe introduced from the top of vessel l in the resulting annular spacebetween the vessel wall and the sieve, and that the bottom 3 remainspartly free of the sieve 2, namely in an annular area along the bottomend of the vessel wall.

Above sieve 2 is arranged a pipe line 5 through which flows a mixture ofwater and solid substances, such as ion exchange resins and filter mud,into the sieve. The filtered water passing through sieve 2 into vessel 1accumulates on the bottom 3 and is drained from there, preferablycontinually, through the suction pipe line 4. As soon as the sieve isfil ed with the solid substances and the water is drained off, drainpipe 4 is removed. Then the remaining cavities, particularly thecylindrical cavity between the vessel wall and the sieve, is filled witha waterbinding and ionizing radiation-absorbing agent, for example,cement broth issuing from another pipe line 6. This measure, by bindingthe remaining water, provides additional protection against corrosion,also additional shielding of ionizing rays of the solid substances andadditional tightness of the vessel. Finally the vessel is tightly sealedwith a cover (not represented) and brought to the provided storageplace.

Another embodiment of the apparatus has, according to FIG. 2, again thevessel 1 provided for storing the solid substances. Inside vessel 1 isarranged a filter bag 8, which is preferably a paper or cloth filter andwhich is suspended in the upper part of the vessel. At this end the topside of the vessel is closed with a cover consisting of an outer ring 9and an inner conical plug 10. The upper edge of filter bag 8 is clampedbetween the conical faces of ring 9 and of plug 10. This clamping devicecan be a pneumatic device, for example. The length of filter bag 8 is sodimensioned that the bottom 3 remains free.

In plug 10 is arranged a central pipe I1 through which the mixture ofwater and solid substances flow into filter bag 8. The wateraccumulating on bottom 3 after the filtering 3 is drained off,preferably continuously, through pipe line 4 arranged vertically alongthe inner wall of vessel 1, which passes through an opening in the coverring 9.

In order to accelerate the filtering, an overpressure can be produced inthe filter bag. This can be achieved, for example, by over-pressure inthe mixture water/solid substances itself, or, after closing pipe line11, by injecting compressed air, to which end a pipe 12 is supportedcoaxially within pipe line 1 l. The compressed air can also beintroduced directly into the liquid which results in a turbulence of thesolid substances in the water. Plug 10 must be tightly scaling in thisapparatus.

If desired, in order to reduce further the water content of the solidsubstances contained in filter bag 8, the contents of the filter bag canbe centrifuged. This is effected in a simple manner in vessel 1 itselfby removing pipe lines 4, 11 and 12 and placing vessel 1, which is, forexample, a commercial barrel, on a turntable provided with acorresponding centrifuge and rotating it about its own longitudinalaxis. The water still contained in filter bag 8 is thus forced to theoutside by the filter bag and accumulates, particularly after theturntable has stopped, on bottom 3, from where it is drained off byinserting again line 4. In order to prevent filter bag 8 from turningeccentrically during centrifuging and from breaking, it is of advantageto surround it with a strong but water-permeable shell 13. This shellcan be, for example, a sufiiciently strong mesh which is placed invessel 1 and into which the filter bag 8 is introduced tightly huggingthe bag, the foraminous shell 13 standing on the bottom wall 3 of vessel1.

In a similar manner can also be centrifuged the solid substancescontained in sieve 2 in the apparatus represented in FIG. 1.

After the filtering and centrifuging respectively and draining of thewater accumulated on bottom 3, a residual water binding and/or ionizingradiation-absorbing agent, like cement broth, can be introduced in theembodiment represented in FIG. 2, through a corresponding pipe line intothe remaining cavities. Vessel 1 is then again tightly sealed andbrought to the provided storage place.

Other liquids, like solutions, acidor alkali-containing liquids, canalso be separated in an advantageous manner with the above describedapparatus from the solid substances contained therein, if the latter areto be stored in tightly sealed vessels and manipulation of the solidsubstances such as transferring, transporting etc. is to be avoidedbecause of its dangerous nature, for example, because of high toxicityetc.

In the above described process, the necessity of a further transfer ofthe mixture liquid/solids or of the solids from the above mentionedcollecting tanks or decaying tanks, if any, to intermediate tanks withthe resulting decanting or transportation is completely avoided. Inparticular the solid substances are in any phase of the process, untilthey have arrived in the vessel.for final storage, in a form in whichthey are easy to transport, for example, to pump, and in which they canbe readily removed to clean the parts of the plants. Apart from theeasy-to-clean pipe lines for filling the vessel and draining off theliquid obtained there are no devices that need attendance. The costs forlost filter means inserted in the vessel, such as the sieve or filterbag, are very low. Besides, there are no investments necessary forcentrifuging and for maintenance work for a centrifuge vessel, requiredheretofore.

We claim:

1. The method for separating liquids from radioactive contaminatedsolids such as that produced in connection with the operation of anuclear power plant and for subsequently storing the filtered out solidswhich comprises the steps of introducing the liquid-solids mixture intoa combined filtering and storage vessel wherein the solids are retainedwithin a filter component spaced from the wall of the vessel, removingthe liquid from the vessel, introducing a water binding and radiationabsorbing cement broth into said space between the filter component andvessel wall after the liquid has been removed to provide protectionagainst corrosion of the vessel and additional shielding for thecontaminated filtered out solids, and thereafter sealing the vessel forstorage.

